AOL has never quite worked as planned for Time Warner, Inc (NYSE: TWX). The merger of the two companies is seen as the cause of the drop in TWX stock to today's $19 -- much improved from earlier this year, but still well below $91, where it traded over six years ago. AOL is taking a large risk by trying to migrate from a subscriber-based revenue model to one driven by ad revenue.

It is hard to say what AOL is worth. One way to look at it: With Time Warner's market cap at $77 billion and AOL representing about 20% of revenue, the company might fetch $15 billion, depending on whether any of Time Warner's debt is involved. Since AOL is in transition, TWX might even sell the company for less.